First, I'm not pushing the limits. Map makers the caliber of Lethal do that. I just work with what I got.
Visuals matter. I refuse to have an invincible battlecruiser for 5 seconds be a spell. I flat out refuse.
The restrictions are a necessary evil. Some other stuff is done already, and every completed aspect of the map enforces its own unique restriction. If I could get around it, I totally would.
Hotkey and mouse usage is completely natural. Have you played Diablo 2 at all? With default controls, you first press F1-12 to select the spell, then right click. That or select the spell with F1-12 before holding shift and left clicking. The system I'm advocating requires some extra action (you have to "reselect" the spell each time before you right click, then select your hero again afterwards), but the difference is minute if you have reasonably fast finger speeds (if you don't, Starcraft isn't the game for you).
I'm leaning toward the Waypoint Casting System, which uses shift and right click to aim the spell. It is therefore a combination of mouse (aiming) and keyboard (hotkey and shift). The Hatchery system requires that you move the mouse out of battle to the bottom right control area. For the pace of gameplay I'm aiming for, the player should not have to mouse their mouse from the battle. It's why I think the Dropship system sucks. Waypoint Casting does everything better than a Hatchery one, though it has its faults. It also allows for more accuracy than an 8 way system as I can achieve angles the other can't and is a lot faster to cast to boot.
The gameplay might be a bit awkward at first, as is any new game, but it isn't that hard to adjust. The point of my demos was to test the spells in actual combat against a group of enemies. I didn't want it to be impossible to play. Player 3 is considered the most click intensive of the characters, and therefore possibly the hardest to play, but in a few minutes of completing him I managed to spam alternating spells at great speeds. I've tested and confirmed that it's doable. You just have to be decently proficient at Starcraft. I'm not catering to the average battle net player. Players who are better at the game should be rewarded. People who aren't can simply build easier characters with more defense and less effective but easier to use offensive spells. Player 3 maxing life, Infested Kerrigan HP, and then 1 offensive spell is one example of an easy build. Player 2 maxing life, range, and strafe is another. They will kill slower of course, but they're easy to play. I was looking for a combat intensive SC RPG, but none achieved the level that I was hoping for. It's why I started the map in the first place.
Spells must come out as exact as possible. I have already made some allowances with Sunkens not always being in the center and Disruption Web sometimes being off by a tile or so when aimed above the Corsair, but it should be pretty damn accurate. Practically every spell I've made requires some form of additional input from the user; no spell should be braindead easy to use. You have to aim some spells, time others, continually switch between them, and sometimes even combo them together. It's why I completely scrapped a large number of spells that I completed, tested, and realized were just far too easy. Healing spells are too easy. Invincible Mutalisks above your head are too easy. So on and so forth.
Ground gridding is a nono. Terrain issues galore. Units in the way issues. For crying out loud, Player 3 can SPAM unburrowing Infested Terrans until there is 0 room for any new unit, unless it's aerial, burrowed, or a powerup, to be created. If I was player 1, I'd sure as hell want to escape with a nice movement spell right then and there, which unplacable spider mines can't provide. In addition, that isn't even counting what enemies can do. The fights I'm planning on are supposed to be large in scale. You're going to be literally mowing down legions of organized enemies here, not some inconsequential wild animal that happened to wander into your path. If you're surrounded (I do want to allow for close ranged builds after all), you need an option to back off immediately.
Oh and, flashstep is a sorry excuse to save money on animation. It doesn't even look cool.
None.